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      1 //===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #include "llvm/MC/MCExpr.h"
     10 #include "llvm/ADT/Statistic.h"
     11 #include "llvm/ADT/StringExtras.h"
     12 #include "llvm/ADT/StringSwitch.h"
     13 #include "llvm/Config/llvm-config.h"
     14 #include "llvm/MC/MCAsmBackend.h"
     15 #include "llvm/MC/MCAsmInfo.h"
     16 #include "llvm/MC/MCAsmLayout.h"
     17 #include "llvm/MC/MCAssembler.h"
     18 #include "llvm/MC/MCContext.h"
     19 #include "llvm/MC/MCObjectWriter.h"
     20 #include "llvm/MC/MCSymbol.h"
     21 #include "llvm/MC/MCValue.h"
     22 #include "llvm/Support/Casting.h"
     23 #include "llvm/Support/Compiler.h"
     24 #include "llvm/Support/Debug.h"
     25 #include "llvm/Support/ErrorHandling.h"
     26 #include "llvm/Support/raw_ostream.h"
     27 #include <cassert>
     28 #include <cstdint>
     29 
     30 using namespace llvm;
     31 
     32 #define DEBUG_TYPE "mcexpr"
     33 
     34 namespace {
     35 namespace stats {
     36 
     37 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
     38 
     39 } // end namespace stats
     40 } // end anonymous namespace
     41 
     42 void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
     43   switch (getKind()) {
     44   case MCExpr::Target:
     45     return cast<MCTargetExpr>(this)->printImpl(OS, MAI);
     46   case MCExpr::Constant: {
     47     auto Value = cast<MCConstantExpr>(*this).getValue();
     48     auto PrintInHex = cast<MCConstantExpr>(*this).useHexFormat();
     49     auto SizeInBytes = cast<MCConstantExpr>(*this).getSizeInBytes();
     50     if (Value < 0 && MAI && !MAI->supportsSignedData())
     51       PrintInHex = true;
     52     if (PrintInHex)
     53       switch (SizeInBytes) {
     54       default:
     55         OS << "0x" << Twine::utohexstr(Value);
     56         break;
     57       case 1:
     58         OS << format("0x%02" PRIx64, Value);
     59         break;
     60       case 2:
     61         OS << format("0x%04" PRIx64, Value);
     62         break;
     63       case 4:
     64         OS << format("0x%08" PRIx64, Value);
     65         break;
     66       case 8:
     67         OS << format("0x%016" PRIx64, Value);
     68         break;
     69       }
     70     else
     71       OS << Value;
     72     return;
     73   }
     74   case MCExpr::SymbolRef: {
     75     const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this);
     76     const MCSymbol &Sym = SRE.getSymbol();
     77     // Parenthesize names that start with $ so that they don't look like
     78     // absolute names.
     79     bool UseParens =
     80         !InParens && !Sym.getName().empty() && Sym.getName()[0] == '$';
     81     if (UseParens) {
     82       OS << '(';
     83       Sym.print(OS, MAI);
     84       OS << ')';
     85     } else
     86       Sym.print(OS, MAI);
     87 
     88     const MCSymbolRefExpr::VariantKind Kind = SRE.getKind();
     89     if (Kind != MCSymbolRefExpr::VK_None) {
     90       if (MAI && MAI->useParensForSymbolVariant()) // ARM
     91         OS << '(' << MCSymbolRefExpr::getVariantKindName(Kind) << ')';
     92       else
     93         OS << '@' << MCSymbolRefExpr::getVariantKindName(Kind);
     94     }
     95 
     96     return;
     97   }
     98 
     99   case MCExpr::Unary: {
    100     const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
    101     switch (UE.getOpcode()) {
    102     case MCUnaryExpr::LNot:  OS << '!'; break;
    103     case MCUnaryExpr::Minus: OS << '-'; break;
    104     case MCUnaryExpr::Not:   OS << '~'; break;
    105     case MCUnaryExpr::Plus:  OS << '+'; break;
    106     }
    107     bool Binary = UE.getSubExpr()->getKind() == MCExpr::Binary;
    108     if (Binary) OS << "(";
    109     UE.getSubExpr()->print(OS, MAI);
    110     if (Binary) OS << ")";
    111     return;
    112   }
    113 
    114   case MCExpr::Binary: {
    115     const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
    116 
    117     // Only print parens around the LHS if it is non-trivial.
    118     if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
    119       BE.getLHS()->print(OS, MAI);
    120     } else {
    121       OS << '(';
    122       BE.getLHS()->print(OS, MAI);
    123       OS << ')';
    124     }
    125 
    126     switch (BE.getOpcode()) {
    127     case MCBinaryExpr::Add:
    128       // Print "X-42" instead of "X+-42".
    129       if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
    130         if (RHSC->getValue() < 0) {
    131           OS << RHSC->getValue();
    132           return;
    133         }
    134       }
    135 
    136       OS <<  '+';
    137       break;
    138     case MCBinaryExpr::AShr: OS << ">>"; break;
    139     case MCBinaryExpr::And:  OS <<  '&'; break;
    140     case MCBinaryExpr::Div:  OS <<  '/'; break;
    141     case MCBinaryExpr::EQ:   OS << "=="; break;
    142     case MCBinaryExpr::GT:   OS <<  '>'; break;
    143     case MCBinaryExpr::GTE:  OS << ">="; break;
    144     case MCBinaryExpr::LAnd: OS << "&&"; break;
    145     case MCBinaryExpr::LOr:  OS << "||"; break;
    146     case MCBinaryExpr::LShr: OS << ">>"; break;
    147     case MCBinaryExpr::LT:   OS <<  '<'; break;
    148     case MCBinaryExpr::LTE:  OS << "<="; break;
    149     case MCBinaryExpr::Mod:  OS <<  '%'; break;
    150     case MCBinaryExpr::Mul:  OS <<  '*'; break;
    151     case MCBinaryExpr::NE:   OS << "!="; break;
    152     case MCBinaryExpr::Or:   OS <<  '|'; break;
    153     case MCBinaryExpr::OrNot: OS << '!'; break;
    154     case MCBinaryExpr::Shl:  OS << "<<"; break;
    155     case MCBinaryExpr::Sub:  OS <<  '-'; break;
    156     case MCBinaryExpr::Xor:  OS <<  '^'; break;
    157     }
    158 
    159     // Only print parens around the LHS if it is non-trivial.
    160     if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
    161       BE.getRHS()->print(OS, MAI);
    162     } else {
    163       OS << '(';
    164       BE.getRHS()->print(OS, MAI);
    165       OS << ')';
    166     }
    167     return;
    168   }
    169   }
    170 
    171   llvm_unreachable("Invalid expression kind!");
    172 }
    173 
    174 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    175 LLVM_DUMP_METHOD void MCExpr::dump() const {
    176   dbgs() << *this;
    177   dbgs() << '\n';
    178 }
    179 #endif
    180 
    181 /* *** */
    182 
    183 const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS,
    184                                          const MCExpr *RHS, MCContext &Ctx,
    185                                          SMLoc Loc) {
    186   return new (Ctx) MCBinaryExpr(Opc, LHS, RHS, Loc);
    187 }
    188 
    189 const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr,
    190                                        MCContext &Ctx, SMLoc Loc) {
    191   return new (Ctx) MCUnaryExpr(Opc, Expr, Loc);
    192 }
    193 
    194 const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx,
    195                                              bool PrintInHex,
    196                                              unsigned SizeInBytes) {
    197   return new (Ctx) MCConstantExpr(Value, PrintInHex, SizeInBytes);
    198 }
    199 
    200 /* *** */
    201 
    202 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
    203                                  const MCAsmInfo *MAI, SMLoc Loc)
    204     : MCExpr(MCExpr::SymbolRef, Loc,
    205              encodeSubclassData(Kind, MAI->hasSubsectionsViaSymbols())),
    206       Symbol(Symbol) {
    207   assert(Symbol);
    208 }
    209 
    210 const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym,
    211                                                VariantKind Kind,
    212                                                MCContext &Ctx, SMLoc Loc) {
    213   return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo(), Loc);
    214 }
    215 
    216 const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind,
    217                                                MCContext &Ctx) {
    218   return create(Ctx.getOrCreateSymbol(Name), Kind, Ctx);
    219 }
    220 
    221 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
    222   switch (Kind) {
    223   case VK_Invalid: return "<<invalid>>";
    224   case VK_None: return "<<none>>";
    225 
    226   case VK_DTPOFF: return "DTPOFF";
    227   case VK_DTPREL: return "DTPREL";
    228   case VK_GOT: return "GOT";
    229   case VK_GOTOFF: return "GOTOFF";
    230   case VK_GOTREL: return "GOTREL";
    231   case VK_PCREL: return "PCREL";
    232   case VK_GOTPCREL: return "GOTPCREL";
    233   case VK_GOTTPOFF: return "GOTTPOFF";
    234   case VK_INDNTPOFF: return "INDNTPOFF";
    235   case VK_NTPOFF: return "NTPOFF";
    236   case VK_GOTNTPOFF: return "GOTNTPOFF";
    237   case VK_PLT: return "PLT";
    238   case VK_TLSGD: return "TLSGD";
    239   case VK_TLSLD: return "TLSLD";
    240   case VK_TLSLDM: return "TLSLDM";
    241   case VK_TPOFF: return "TPOFF";
    242   case VK_TPREL: return "TPREL";
    243   case VK_TLSCALL: return "tlscall";
    244   case VK_TLSDESC: return "tlsdesc";
    245   case VK_TLVP: return "TLVP";
    246   case VK_TLVPPAGE: return "TLVPPAGE";
    247   case VK_TLVPPAGEOFF: return "TLVPPAGEOFF";
    248   case VK_PAGE: return "PAGE";
    249   case VK_PAGEOFF: return "PAGEOFF";
    250   case VK_GOTPAGE: return "GOTPAGE";
    251   case VK_GOTPAGEOFF: return "GOTPAGEOFF";
    252   case VK_SECREL: return "SECREL32";
    253   case VK_SIZE: return "SIZE";
    254   case VK_WEAKREF: return "WEAKREF";
    255   case VK_X86_ABS8: return "ABS8";
    256   case VK_X86_PLTOFF: return "PLTOFF";
    257   case VK_ARM_NONE: return "none";
    258   case VK_ARM_GOT_PREL: return "GOT_PREL";
    259   case VK_ARM_TARGET1: return "target1";
    260   case VK_ARM_TARGET2: return "target2";
    261   case VK_ARM_PREL31: return "prel31";
    262   case VK_ARM_SBREL: return "sbrel";
    263   case VK_ARM_TLSLDO: return "tlsldo";
    264   case VK_ARM_TLSDESCSEQ: return "tlsdescseq";
    265   case VK_AVR_NONE: return "none";
    266   case VK_AVR_LO8: return "lo8";
    267   case VK_AVR_HI8: return "hi8";
    268   case VK_AVR_HLO8: return "hlo8";
    269   case VK_AVR_DIFF8: return "diff8";
    270   case VK_AVR_DIFF16: return "diff16";
    271   case VK_AVR_DIFF32: return "diff32";
    272   case VK_AVR_PM: return "pm";
    273   case VK_PPC_LO: return "l";
    274   case VK_PPC_HI: return "h";
    275   case VK_PPC_HA: return "ha";
    276   case VK_PPC_HIGH: return "high";
    277   case VK_PPC_HIGHA: return "higha";
    278   case VK_PPC_HIGHER: return "higher";
    279   case VK_PPC_HIGHERA: return "highera";
    280   case VK_PPC_HIGHEST: return "highest";
    281   case VK_PPC_HIGHESTA: return "highesta";
    282   case VK_PPC_GOT_LO: return "got@l";
    283   case VK_PPC_GOT_HI: return "got@h";
    284   case VK_PPC_GOT_HA: return "got@ha";
    285   case VK_PPC_TOCBASE: return "tocbase";
    286   case VK_PPC_TOC: return "toc";
    287   case VK_PPC_TOC_LO: return "toc@l";
    288   case VK_PPC_TOC_HI: return "toc@h";
    289   case VK_PPC_TOC_HA: return "toc@ha";
    290   case VK_PPC_U: return "u";
    291   case VK_PPC_L: return "l";
    292   case VK_PPC_DTPMOD: return "dtpmod";
    293   case VK_PPC_TPREL_LO: return "tprel@l";
    294   case VK_PPC_TPREL_HI: return "tprel@h";
    295   case VK_PPC_TPREL_HA: return "tprel@ha";
    296   case VK_PPC_TPREL_HIGH: return "tprel@high";
    297   case VK_PPC_TPREL_HIGHA: return "tprel@higha";
    298   case VK_PPC_TPREL_HIGHER: return "tprel@higher";
    299   case VK_PPC_TPREL_HIGHERA: return "tprel@highera";
    300   case VK_PPC_TPREL_HIGHEST: return "tprel@highest";
    301   case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta";
    302   case VK_PPC_DTPREL_LO: return "dtprel@l";
    303   case VK_PPC_DTPREL_HI: return "dtprel@h";
    304   case VK_PPC_DTPREL_HA: return "dtprel@ha";
    305   case VK_PPC_DTPREL_HIGH: return "dtprel@high";
    306   case VK_PPC_DTPREL_HIGHA: return "dtprel@higha";
    307   case VK_PPC_DTPREL_HIGHER: return "dtprel@higher";
    308   case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera";
    309   case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest";
    310   case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta";
    311   case VK_PPC_GOT_TPREL: return "got@tprel";
    312   case VK_PPC_GOT_TPREL_LO: return "got@tprel@l";
    313   case VK_PPC_GOT_TPREL_HI: return "got@tprel@h";
    314   case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha";
    315   case VK_PPC_GOT_DTPREL: return "got@dtprel";
    316   case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l";
    317   case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h";
    318   case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha";
    319   case VK_PPC_TLS: return "tls";
    320   case VK_PPC_GOT_TLSGD: return "got@tlsgd";
    321   case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l";
    322   case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h";
    323   case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha";
    324   case VK_PPC_TLSGD: return "tlsgd";
    325   case VK_PPC_AIX_TLSGD:
    326     return "gd";
    327   case VK_PPC_AIX_TLSGDM:
    328     return "m";
    329   case VK_PPC_GOT_TLSLD: return "got@tlsld";
    330   case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l";
    331   case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h";
    332   case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha";
    333   case VK_PPC_GOT_PCREL:
    334     return "got@pcrel";
    335   case VK_PPC_GOT_TLSGD_PCREL:
    336     return "got@tlsgd@pcrel";
    337   case VK_PPC_GOT_TLSLD_PCREL:
    338     return "got@tlsld@pcrel";
    339   case VK_PPC_GOT_TPREL_PCREL:
    340     return "got@tprel@pcrel";
    341   case VK_PPC_TLS_PCREL:
    342     return "tls@pcrel";
    343   case VK_PPC_TLSLD: return "tlsld";
    344   case VK_PPC_LOCAL: return "local";
    345   case VK_PPC_NOTOC: return "notoc";
    346   case VK_PPC_PCREL_OPT: return "<<invalid>>";
    347   case VK_COFF_IMGREL32: return "IMGREL";
    348   case VK_Hexagon_LO16: return "LO16";
    349   case VK_Hexagon_HI16: return "HI16";
    350   case VK_Hexagon_GPREL: return "GPREL";
    351   case VK_Hexagon_GD_GOT: return "GDGOT";
    352   case VK_Hexagon_LD_GOT: return "LDGOT";
    353   case VK_Hexagon_GD_PLT: return "GDPLT";
    354   case VK_Hexagon_LD_PLT: return "LDPLT";
    355   case VK_Hexagon_IE: return "IE";
    356   case VK_Hexagon_IE_GOT: return "IEGOT";
    357   case VK_WASM_TYPEINDEX: return "TYPEINDEX";
    358   case VK_WASM_MBREL: return "MBREL";
    359   case VK_WASM_TLSREL: return "TLSREL";
    360   case VK_WASM_TBREL: return "TBREL";
    361   case VK_AMDGPU_GOTPCREL32_LO: return "gotpcrel32@lo";
    362   case VK_AMDGPU_GOTPCREL32_HI: return "gotpcrel32@hi";
    363   case VK_AMDGPU_REL32_LO: return "rel32@lo";
    364   case VK_AMDGPU_REL32_HI: return "rel32@hi";
    365   case VK_AMDGPU_REL64: return "rel64";
    366   case VK_AMDGPU_ABS32_LO: return "abs32@lo";
    367   case VK_AMDGPU_ABS32_HI: return "abs32@hi";
    368   case VK_VE_HI32: return "hi";
    369   case VK_VE_LO32: return "lo";
    370   case VK_VE_PC_HI32: return "pc_hi";
    371   case VK_VE_PC_LO32: return "pc_lo";
    372   case VK_VE_GOT_HI32: return "got_hi";
    373   case VK_VE_GOT_LO32: return "got_lo";
    374   case VK_VE_GOTOFF_HI32: return "gotoff_hi";
    375   case VK_VE_GOTOFF_LO32: return "gotoff_lo";
    376   case VK_VE_PLT_HI32: return "plt_hi";
    377   case VK_VE_PLT_LO32: return "plt_lo";
    378   case VK_VE_TLS_GD_HI32: return "tls_gd_hi";
    379   case VK_VE_TLS_GD_LO32: return "tls_gd_lo";
    380   case VK_VE_TPOFF_HI32: return "tpoff_hi";
    381   case VK_VE_TPOFF_LO32: return "tpoff_lo";
    382   }
    383   llvm_unreachable("Invalid variant kind");
    384 }
    385 
    386 MCSymbolRefExpr::VariantKind
    387 MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
    388   return StringSwitch<VariantKind>(Name.lower())
    389     .Case("dtprel", VK_DTPREL)
    390     .Case("dtpoff", VK_DTPOFF)
    391     .Case("got", VK_GOT)
    392     .Case("gotoff", VK_GOTOFF)
    393     .Case("gotrel", VK_GOTREL)
    394     .Case("pcrel", VK_PCREL)
    395     .Case("gotpcrel", VK_GOTPCREL)
    396     .Case("gottpoff", VK_GOTTPOFF)
    397     .Case("indntpoff", VK_INDNTPOFF)
    398     .Case("ntpoff", VK_NTPOFF)
    399     .Case("gotntpoff", VK_GOTNTPOFF)
    400     .Case("plt", VK_PLT)
    401     .Case("tlscall", VK_TLSCALL)
    402     .Case("tlsdesc", VK_TLSDESC)
    403     .Case("tlsgd", VK_TLSGD)
    404     .Case("tlsld", VK_TLSLD)
    405     .Case("tlsldm", VK_TLSLDM)
    406     .Case("tpoff", VK_TPOFF)
    407     .Case("tprel", VK_TPREL)
    408     .Case("tlvp", VK_TLVP)
    409     .Case("tlvppage", VK_TLVPPAGE)
    410     .Case("tlvppageoff", VK_TLVPPAGEOFF)
    411     .Case("page", VK_PAGE)
    412     .Case("pageoff", VK_PAGEOFF)
    413     .Case("gotpage", VK_GOTPAGE)
    414     .Case("gotpageoff", VK_GOTPAGEOFF)
    415     .Case("imgrel", VK_COFF_IMGREL32)
    416     .Case("secrel32", VK_SECREL)
    417     .Case("size", VK_SIZE)
    418     .Case("abs8", VK_X86_ABS8)
    419     .Case("pltoff", VK_X86_PLTOFF)
    420     .Case("l", VK_PPC_LO)
    421     .Case("h", VK_PPC_HI)
    422     .Case("ha", VK_PPC_HA)
    423     .Case("high", VK_PPC_HIGH)
    424     .Case("higha", VK_PPC_HIGHA)
    425     .Case("higher", VK_PPC_HIGHER)
    426     .Case("highera", VK_PPC_HIGHERA)
    427     .Case("highest", VK_PPC_HIGHEST)
    428     .Case("highesta", VK_PPC_HIGHESTA)
    429     .Case("got@l", VK_PPC_GOT_LO)
    430     .Case("got@h", VK_PPC_GOT_HI)
    431     .Case("got@ha", VK_PPC_GOT_HA)
    432     .Case("local", VK_PPC_LOCAL)
    433     .Case("tocbase", VK_PPC_TOCBASE)
    434     .Case("toc", VK_PPC_TOC)
    435     .Case("toc@l", VK_PPC_TOC_LO)
    436     .Case("toc@h", VK_PPC_TOC_HI)
    437     .Case("toc@ha", VK_PPC_TOC_HA)
    438     .Case("u", VK_PPC_U)
    439     .Case("l", VK_PPC_L)
    440     .Case("tls", VK_PPC_TLS)
    441     .Case("dtpmod", VK_PPC_DTPMOD)
    442     .Case("tprel@l", VK_PPC_TPREL_LO)
    443     .Case("tprel@h", VK_PPC_TPREL_HI)
    444     .Case("tprel@ha", VK_PPC_TPREL_HA)
    445     .Case("tprel@high", VK_PPC_TPREL_HIGH)
    446     .Case("tprel@higha", VK_PPC_TPREL_HIGHA)
    447     .Case("tprel@higher", VK_PPC_TPREL_HIGHER)
    448     .Case("tprel@highera", VK_PPC_TPREL_HIGHERA)
    449     .Case("tprel@highest", VK_PPC_TPREL_HIGHEST)
    450     .Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA)
    451     .Case("dtprel@l", VK_PPC_DTPREL_LO)
    452     .Case("dtprel@h", VK_PPC_DTPREL_HI)
    453     .Case("dtprel@ha", VK_PPC_DTPREL_HA)
    454     .Case("dtprel@high", VK_PPC_DTPREL_HIGH)
    455     .Case("dtprel@higha", VK_PPC_DTPREL_HIGHA)
    456     .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER)
    457     .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA)
    458     .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST)
    459     .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA)
    460     .Case("got@tprel", VK_PPC_GOT_TPREL)
    461     .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO)
    462     .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI)
    463     .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA)
    464     .Case("got@dtprel", VK_PPC_GOT_DTPREL)
    465     .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO)
    466     .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI)
    467     .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA)
    468     .Case("got@tlsgd", VK_PPC_GOT_TLSGD)
    469     .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO)
    470     .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI)
    471     .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA)
    472     .Case("got@tlsld", VK_PPC_GOT_TLSLD)
    473     .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO)
    474     .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI)
    475     .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA)
    476     .Case("got@pcrel", VK_PPC_GOT_PCREL)
    477     .Case("got@tlsgd@pcrel", VK_PPC_GOT_TLSGD_PCREL)
    478     .Case("got@tlsld@pcrel", VK_PPC_GOT_TLSLD_PCREL)
    479     .Case("got@tprel@pcrel", VK_PPC_GOT_TPREL_PCREL)
    480     .Case("tls@pcrel", VK_PPC_TLS_PCREL)
    481     .Case("notoc", VK_PPC_NOTOC)
    482     .Case("gdgot", VK_Hexagon_GD_GOT)
    483     .Case("gdplt", VK_Hexagon_GD_PLT)
    484     .Case("iegot", VK_Hexagon_IE_GOT)
    485     .Case("ie", VK_Hexagon_IE)
    486     .Case("ldgot", VK_Hexagon_LD_GOT)
    487     .Case("ldplt", VK_Hexagon_LD_PLT)
    488     .Case("none", VK_ARM_NONE)
    489     .Case("got_prel", VK_ARM_GOT_PREL)
    490     .Case("target1", VK_ARM_TARGET1)
    491     .Case("target2", VK_ARM_TARGET2)
    492     .Case("prel31", VK_ARM_PREL31)
    493     .Case("sbrel", VK_ARM_SBREL)
    494     .Case("tlsldo", VK_ARM_TLSLDO)
    495     .Case("lo8", VK_AVR_LO8)
    496     .Case("hi8", VK_AVR_HI8)
    497     .Case("hlo8", VK_AVR_HLO8)
    498     .Case("typeindex", VK_WASM_TYPEINDEX)
    499     .Case("tbrel", VK_WASM_TBREL)
    500     .Case("mbrel", VK_WASM_MBREL)
    501     .Case("tlsrel", VK_WASM_TLSREL)
    502     .Case("gotpcrel32@lo", VK_AMDGPU_GOTPCREL32_LO)
    503     .Case("gotpcrel32@hi", VK_AMDGPU_GOTPCREL32_HI)
    504     .Case("rel32@lo", VK_AMDGPU_REL32_LO)
    505     .Case("rel32@hi", VK_AMDGPU_REL32_HI)
    506     .Case("rel64", VK_AMDGPU_REL64)
    507     .Case("abs32@lo", VK_AMDGPU_ABS32_LO)
    508     .Case("abs32@hi", VK_AMDGPU_ABS32_HI)
    509     .Case("hi", VK_VE_HI32)
    510     .Case("lo", VK_VE_LO32)
    511     .Case("pc_hi", VK_VE_PC_HI32)
    512     .Case("pc_lo", VK_VE_PC_LO32)
    513     .Case("got_hi", VK_VE_GOT_HI32)
    514     .Case("got_lo", VK_VE_GOT_LO32)
    515     .Case("gotoff_hi", VK_VE_GOTOFF_HI32)
    516     .Case("gotoff_lo", VK_VE_GOTOFF_LO32)
    517     .Case("plt_hi", VK_VE_PLT_HI32)
    518     .Case("plt_lo", VK_VE_PLT_LO32)
    519     .Case("tls_gd_hi", VK_VE_TLS_GD_HI32)
    520     .Case("tls_gd_lo", VK_VE_TLS_GD_LO32)
    521     .Case("tpoff_hi", VK_VE_TPOFF_HI32)
    522     .Case("tpoff_lo", VK_VE_TPOFF_LO32)
    523     .Default(VK_Invalid);
    524 }
    525 
    526 /* *** */
    527 
    528 void MCTargetExpr::anchor() {}
    529 
    530 /* *** */
    531 
    532 bool MCExpr::evaluateAsAbsolute(int64_t &Res) const {
    533   return evaluateAsAbsolute(Res, nullptr, nullptr, nullptr, false);
    534 }
    535 
    536 bool MCExpr::evaluateAsAbsolute(int64_t &Res,
    537                                 const MCAsmLayout &Layout) const {
    538   return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, false);
    539 }
    540 
    541 bool MCExpr::evaluateAsAbsolute(int64_t &Res,
    542                                 const MCAsmLayout &Layout,
    543                                 const SectionAddrMap &Addrs) const {
    544   // Setting InSet causes us to absolutize differences across sections and that
    545   // is what the MachO writer uses Addrs for.
    546   return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs, true);
    547 }
    548 
    549 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
    550   return evaluateAsAbsolute(Res, &Asm, nullptr, nullptr, false);
    551 }
    552 
    553 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm) const {
    554   return evaluateAsAbsolute(Res, Asm, nullptr, nullptr, false);
    555 }
    556 
    557 bool MCExpr::evaluateKnownAbsolute(int64_t &Res,
    558                                    const MCAsmLayout &Layout) const {
    559   return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr,
    560                             true);
    561 }
    562 
    563 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
    564                                 const MCAsmLayout *Layout,
    565                                 const SectionAddrMap *Addrs, bool InSet) const {
    566   MCValue Value;
    567 
    568   // Fast path constants.
    569   if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
    570     Res = CE->getValue();
    571     return true;
    572   }
    573 
    574   bool IsRelocatable =
    575       evaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet);
    576 
    577   // Record the current value.
    578   Res = Value.getConstant();
    579 
    580   return IsRelocatable && Value.isAbsolute();
    581 }
    582 
    583 /// Helper method for \see EvaluateSymbolAdd().
    584 static void AttemptToFoldSymbolOffsetDifference(
    585     const MCAssembler *Asm, const MCAsmLayout *Layout,
    586     const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A,
    587     const MCSymbolRefExpr *&B, int64_t &Addend) {
    588   if (!A || !B)
    589     return;
    590 
    591   const MCSymbol &SA = A->getSymbol();
    592   const MCSymbol &SB = B->getSymbol();
    593 
    594   if (SA.isUndefined() || SB.isUndefined())
    595     return;
    596 
    597   if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
    598     return;
    599 
    600   auto FinalizeFolding = [&]() {
    601     // Pointers to Thumb symbols need to have their low-bit set to allow
    602     // for interworking.
    603     if (Asm->isThumbFunc(&SA))
    604       Addend |= 1;
    605 
    606     // If symbol is labeled as micromips, we set low-bit to ensure
    607     // correct offset in .gcc_except_table
    608     if (Asm->getBackend().isMicroMips(&SA))
    609       Addend |= 1;
    610 
    611     // Clear the symbol expr pointers to indicate we have folded these
    612     // operands.
    613     A = B = nullptr;
    614   };
    615 
    616   const MCFragment *FA = SA.getFragment();
    617   const MCFragment *FB = SB.getFragment();
    618   // If both symbols are in the same fragment, return the difference of their
    619   // offsets
    620   if (FA == FB && !SA.isVariable() && !SA.isUnset() && !SB.isVariable() &&
    621       !SB.isUnset()) {
    622     Addend += SA.getOffset() - SB.getOffset();
    623     return FinalizeFolding();
    624   }
    625 
    626   const MCSection &SecA = *FA->getParent();
    627   const MCSection &SecB = *FB->getParent();
    628 
    629   if ((&SecA != &SecB) && !Addrs)
    630     return;
    631 
    632   if (Layout) {
    633     // One of the symbol involved is part of a fragment being laid out. Quit now
    634     // to avoid a self loop.
    635     if (!Layout->canGetFragmentOffset(FA) || !Layout->canGetFragmentOffset(FB))
    636       return;
    637 
    638     // Eagerly evaluate when layout is finalized.
    639     Addend += Layout->getSymbolOffset(A->getSymbol()) -
    640               Layout->getSymbolOffset(B->getSymbol());
    641     if (Addrs && (&SecA != &SecB))
    642       Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
    643 
    644     FinalizeFolding();
    645   } else {
    646     // When layout is not finalized, our ability to resolve differences between
    647     // symbols is limited to specific cases where the fragments between two
    648     // symbols (including the fragments the symbols are defined in) are
    649     // fixed-size fragments so the difference can be calculated. For example,
    650     // this is important when the Subtarget is changed and a new MCDataFragment
    651     // is created in the case of foo: instr; .arch_extension ext; instr .if . -
    652     // foo.
    653     if (SA.isVariable() || SA.isUnset() || SB.isVariable() || SB.isUnset() ||
    654         FA->getKind() != MCFragment::FT_Data ||
    655         FB->getKind() != MCFragment::FT_Data ||
    656         FA->getSubsectionNumber() != FB->getSubsectionNumber())
    657       return;
    658     // Try to find a constant displacement from FA to FB, add the displacement
    659     // between the offset in FA of SA and the offset in FB of SB.
    660     int64_t Displacement = SA.getOffset() - SB.getOffset();
    661     for (auto FI = FB->getIterator(), FE = SecA.end(); FI != FE; ++FI) {
    662       if (&*FI == FA) {
    663         Addend += Displacement;
    664         return FinalizeFolding();
    665       }
    666 
    667       if (FI->getKind() != MCFragment::FT_Data)
    668         return;
    669       Displacement += cast<MCDataFragment>(FI)->getContents().size();
    670     }
    671   }
    672 }
    673 
    674 static bool canFold(const MCAssembler *Asm, const MCSymbolRefExpr *A,
    675                     const MCSymbolRefExpr *B, bool InSet) {
    676   if (InSet)
    677     return true;
    678 
    679   if (!Asm->getBackend().requiresDiffExpressionRelocations())
    680     return true;
    681 
    682   const MCSymbol &CheckSym = A ? A->getSymbol() : B->getSymbol();
    683   if (!CheckSym.isInSection())
    684     return true;
    685 
    686   if (!CheckSym.getSection().hasInstructions())
    687     return true;
    688 
    689   return false;
    690 }
    691 
    692 /// Evaluate the result of an add between (conceptually) two MCValues.
    693 ///
    694 /// This routine conceptually attempts to construct an MCValue:
    695 ///   Result = (Result_A - Result_B + Result_Cst)
    696 /// from two MCValue's LHS and RHS where
    697 ///   Result = LHS + RHS
    698 /// and
    699 ///   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
    700 ///
    701 /// This routine attempts to aggressively fold the operands such that the result
    702 /// is representable in an MCValue, but may not always succeed.
    703 ///
    704 /// \returns True on success, false if the result is not representable in an
    705 /// MCValue.
    706 
    707 /// NOTE: It is really important to have both the Asm and Layout arguments.
    708 /// They might look redundant, but this function can be used before layout
    709 /// is done (see the object streamer for example) and having the Asm argument
    710 /// lets us avoid relaxations early.
    711 static bool
    712 EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout,
    713                     const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS,
    714                     const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B,
    715                     int64_t RHS_Cst, MCValue &Res) {
    716   // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
    717   // about dealing with modifiers. This will ultimately bite us, one day.
    718   const MCSymbolRefExpr *LHS_A = LHS.getSymA();
    719   const MCSymbolRefExpr *LHS_B = LHS.getSymB();
    720   int64_t LHS_Cst = LHS.getConstant();
    721 
    722   // Fold the result constant immediately.
    723   int64_t Result_Cst = LHS_Cst + RHS_Cst;
    724 
    725   assert((!Layout || Asm) &&
    726          "Must have an assembler object if layout is given!");
    727 
    728   // If we have a layout, we can fold resolved differences. Do not do this if
    729   // the backend requires this to be emitted as individual relocations, unless
    730   // the InSet flag is set to get the current difference anyway (used for
    731   // example to calculate symbol sizes).
    732   if (Asm && canFold(Asm, LHS_A, LHS_B, InSet)) {
    733     // First, fold out any differences which are fully resolved. By
    734     // reassociating terms in
    735     //   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
    736     // we have the four possible differences:
    737     //   (LHS_A - LHS_B),
    738     //   (LHS_A - RHS_B),
    739     //   (RHS_A - LHS_B),
    740     //   (RHS_A - RHS_B).
    741     // Since we are attempting to be as aggressive as possible about folding, we
    742     // attempt to evaluate each possible alternative.
    743     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
    744                                         Result_Cst);
    745     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
    746                                         Result_Cst);
    747     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
    748                                         Result_Cst);
    749     AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
    750                                         Result_Cst);
    751   }
    752 
    753   // We can't represent the addition or subtraction of two symbols.
    754   if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
    755     return false;
    756 
    757   // At this point, we have at most one additive symbol and one subtractive
    758   // symbol -- find them.
    759   const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
    760   const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
    761 
    762   Res = MCValue::get(A, B, Result_Cst);
    763   return true;
    764 }
    765 
    766 bool MCExpr::evaluateAsRelocatable(MCValue &Res,
    767                                    const MCAsmLayout *Layout,
    768                                    const MCFixup *Fixup) const {
    769   MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr;
    770   return evaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr,
    771                                    false);
    772 }
    773 
    774 bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
    775   MCAssembler *Assembler = &Layout.getAssembler();
    776   return evaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr,
    777                                    true);
    778 }
    779 
    780 static bool canExpand(const MCSymbol &Sym, bool InSet) {
    781   const MCExpr *Expr = Sym.getVariableValue();
    782   const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
    783   if (Inner) {
    784     if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
    785       return false;
    786   }
    787 
    788   if (InSet)
    789     return true;
    790   return !Sym.isInSection();
    791 }
    792 
    793 bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
    794                                        const MCAsmLayout *Layout,
    795                                        const MCFixup *Fixup,
    796                                        const SectionAddrMap *Addrs,
    797                                        bool InSet) const {
    798   ++stats::MCExprEvaluate;
    799 
    800   switch (getKind()) {
    801   case Target:
    802     return cast<MCTargetExpr>(this)->evaluateAsRelocatableImpl(Res, Layout,
    803                                                                Fixup);
    804 
    805   case Constant:
    806     Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
    807     return true;
    808 
    809   case SymbolRef: {
    810     const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
    811     const MCSymbol &Sym = SRE->getSymbol();
    812     const auto Kind = SRE->getKind();
    813 
    814     // Evaluate recursively if this is a variable.
    815     if (Sym.isVariable() && (Kind == MCSymbolRefExpr::VK_None || Layout) &&
    816         canExpand(Sym, InSet)) {
    817       bool IsMachO = SRE->hasSubsectionsViaSymbols();
    818       if (Sym.getVariableValue()->evaluateAsRelocatableImpl(
    819               Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) {
    820         if (Kind != MCSymbolRefExpr::VK_None) {
    821           if (Res.isAbsolute()) {
    822             Res = MCValue::get(SRE, nullptr, 0);
    823             return true;
    824           }
    825           // If the reference has a variant kind, we can only handle expressions
    826           // which evaluate exactly to a single unadorned symbol. Attach the
    827           // original VariantKind to SymA of the result.
    828           if (Res.getRefKind() != MCSymbolRefExpr::VK_None || !Res.getSymA() ||
    829               Res.getSymB() || Res.getConstant())
    830             return false;
    831           Res =
    832               MCValue::get(MCSymbolRefExpr::create(&Res.getSymA()->getSymbol(),
    833                                                    Kind, Asm->getContext()),
    834                            Res.getSymB(), Res.getConstant(), Res.getRefKind());
    835         }
    836         if (!IsMachO)
    837           return true;
    838 
    839         const MCSymbolRefExpr *A = Res.getSymA();
    840         const MCSymbolRefExpr *B = Res.getSymB();
    841         // FIXME: This is small hack. Given
    842         // a = b + 4
    843         // .long a
    844         // the OS X assembler will completely drop the 4. We should probably
    845         // include it in the relocation or produce an error if that is not
    846         // possible.
    847         // Allow constant expressions.
    848         if (!A && !B)
    849           return true;
    850         // Allows aliases with zero offset.
    851         if (Res.getConstant() == 0 && (!A || !B))
    852           return true;
    853       }
    854     }
    855 
    856     Res = MCValue::get(SRE, nullptr, 0);
    857     return true;
    858   }
    859 
    860   case Unary: {
    861     const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
    862     MCValue Value;
    863 
    864     if (!AUE->getSubExpr()->evaluateAsRelocatableImpl(Value, Asm, Layout, Fixup,
    865                                                       Addrs, InSet))
    866       return false;
    867 
    868     switch (AUE->getOpcode()) {
    869     case MCUnaryExpr::LNot:
    870       if (!Value.isAbsolute())
    871         return false;
    872       Res = MCValue::get(!Value.getConstant());
    873       break;
    874     case MCUnaryExpr::Minus:
    875       /// -(a - b + const) ==> (b - a - const)
    876       if (Value.getSymA() && !Value.getSymB())
    877         return false;
    878 
    879       // The cast avoids undefined behavior if the constant is INT64_MIN.
    880       Res = MCValue::get(Value.getSymB(), Value.getSymA(),
    881                          -(uint64_t)Value.getConstant());
    882       break;
    883     case MCUnaryExpr::Not:
    884       if (!Value.isAbsolute())
    885         return false;
    886       Res = MCValue::get(~Value.getConstant());
    887       break;
    888     case MCUnaryExpr::Plus:
    889       Res = Value;
    890       break;
    891     }
    892 
    893     return true;
    894   }
    895 
    896   case Binary: {
    897     const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
    898     MCValue LHSValue, RHSValue;
    899 
    900     if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup,
    901                                                   Addrs, InSet) ||
    902         !ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup,
    903                                                   Addrs, InSet)) {
    904       // Check if both are Target Expressions, see if we can compare them.
    905       if (const MCTargetExpr *L = dyn_cast<MCTargetExpr>(ABE->getLHS()))
    906         if (const MCTargetExpr *R = cast<MCTargetExpr>(ABE->getRHS())) {
    907           switch (ABE->getOpcode()) {
    908           case MCBinaryExpr::EQ:
    909             Res = MCValue::get((L->isEqualTo(R)) ? -1 : 0);
    910             return true;
    911           case MCBinaryExpr::NE:
    912             Res = MCValue::get((R->isEqualTo(R)) ? 0 : -1);
    913             return true;
    914           default: break;
    915           }
    916         }
    917       return false;
    918     }
    919 
    920     // We only support a few operations on non-constant expressions, handle
    921     // those first.
    922     if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
    923       switch (ABE->getOpcode()) {
    924       default:
    925         return false;
    926       case MCBinaryExpr::Sub:
    927         // Negate RHS and add.
    928         // The cast avoids undefined behavior if the constant is INT64_MIN.
    929         return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
    930                                    RHSValue.getSymB(), RHSValue.getSymA(),
    931                                    -(uint64_t)RHSValue.getConstant(), Res);
    932 
    933       case MCBinaryExpr::Add:
    934         return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
    935                                    RHSValue.getSymA(), RHSValue.getSymB(),
    936                                    RHSValue.getConstant(), Res);
    937       }
    938     }
    939 
    940     // FIXME: We need target hooks for the evaluation. It may be limited in
    941     // width, and gas defines the result of comparisons differently from
    942     // Apple as.
    943     int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
    944     int64_t Result = 0;
    945     auto Op = ABE->getOpcode();
    946     switch (Op) {
    947     case MCBinaryExpr::AShr: Result = LHS >> RHS; break;
    948     case MCBinaryExpr::Add:  Result = LHS + RHS; break;
    949     case MCBinaryExpr::And:  Result = LHS & RHS; break;
    950     case MCBinaryExpr::Div:
    951     case MCBinaryExpr::Mod:
    952       // Handle division by zero. gas just emits a warning and keeps going,
    953       // we try to be stricter.
    954       // FIXME: Currently the caller of this function has no way to understand
    955       // we're bailing out because of 'division by zero'. Therefore, it will
    956       // emit a 'expected relocatable expression' error. It would be nice to
    957       // change this code to emit a better diagnostic.
    958       if (RHS == 0)
    959         return false;
    960       if (ABE->getOpcode() == MCBinaryExpr::Div)
    961         Result = LHS / RHS;
    962       else
    963         Result = LHS % RHS;
    964       break;
    965     case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
    966     case MCBinaryExpr::GT:   Result = LHS > RHS; break;
    967     case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;
    968     case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
    969     case MCBinaryExpr::LOr:  Result = LHS || RHS; break;
    970     case MCBinaryExpr::LShr: Result = uint64_t(LHS) >> uint64_t(RHS); break;
    971     case MCBinaryExpr::LT:   Result = LHS < RHS; break;
    972     case MCBinaryExpr::LTE:  Result = LHS <= RHS; break;
    973     case MCBinaryExpr::Mul:  Result = LHS * RHS; break;
    974     case MCBinaryExpr::NE:   Result = LHS != RHS; break;
    975     case MCBinaryExpr::Or:   Result = LHS | RHS; break;
    976     case MCBinaryExpr::OrNot: Result = LHS | ~RHS; break;
    977     case MCBinaryExpr::Shl:  Result = uint64_t(LHS) << uint64_t(RHS); break;
    978     case MCBinaryExpr::Sub:  Result = LHS - RHS; break;
    979     case MCBinaryExpr::Xor:  Result = LHS ^ RHS; break;
    980     }
    981 
    982     switch (Op) {
    983     default:
    984       Res = MCValue::get(Result);
    985       break;
    986     case MCBinaryExpr::EQ:
    987     case MCBinaryExpr::GT:
    988     case MCBinaryExpr::GTE:
    989     case MCBinaryExpr::LT:
    990     case MCBinaryExpr::LTE:
    991     case MCBinaryExpr::NE:
    992       // A comparison operator returns a -1 if true and 0 if false.
    993       Res = MCValue::get(Result ? -1 : 0);
    994       break;
    995     }
    996 
    997     return true;
    998   }
    999   }
   1000 
   1001   llvm_unreachable("Invalid assembly expression kind!");
   1002 }
   1003 
   1004 MCFragment *MCExpr::findAssociatedFragment() const {
   1005   switch (getKind()) {
   1006   case Target:
   1007     // We never look through target specific expressions.
   1008     return cast<MCTargetExpr>(this)->findAssociatedFragment();
   1009 
   1010   case Constant:
   1011     return MCSymbol::AbsolutePseudoFragment;
   1012 
   1013   case SymbolRef: {
   1014     const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
   1015     const MCSymbol &Sym = SRE->getSymbol();
   1016     return Sym.getFragment();
   1017   }
   1018 
   1019   case Unary:
   1020     return cast<MCUnaryExpr>(this)->getSubExpr()->findAssociatedFragment();
   1021 
   1022   case Binary: {
   1023     const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
   1024     MCFragment *LHS_F = BE->getLHS()->findAssociatedFragment();
   1025     MCFragment *RHS_F = BE->getRHS()->findAssociatedFragment();
   1026 
   1027     // If either is absolute, return the other.
   1028     if (LHS_F == MCSymbol::AbsolutePseudoFragment)
   1029       return RHS_F;
   1030     if (RHS_F == MCSymbol::AbsolutePseudoFragment)
   1031       return LHS_F;
   1032 
   1033     // Not always correct, but probably the best we can do without more context.
   1034     if (BE->getOpcode() == MCBinaryExpr::Sub)
   1035       return MCSymbol::AbsolutePseudoFragment;
   1036 
   1037     // Otherwise, return the first non-null fragment.
   1038     return LHS_F ? LHS_F : RHS_F;
   1039   }
   1040   }
   1041 
   1042   llvm_unreachable("Invalid assembly expression kind!");
   1043 }
   1044